Conductivity anomalies were observed in mixed, ion-conducting and polaron-conducting, glasses. Deep minima in the conductivity (similar to those caused by the mixed-alkali effect) appeared when small amounts of Li2O were introduced into WO3-P2O5 glasses. It was suggested that negatively charged polarons (d-electrons at a W5+ center) interacted strongly with mobile cations so as to form uncharged mobile entities. It was suggested that this might be a general occurrence in mixed, ionic and electronic, conductors when the mobilities of ions and electrons were comparable in magnitude.

J.C.Bazan, J.A.Duffy, M.D.Ingram, M.R.Mallace: Solid State Ionics, 1996, 86-88[1], 497-501